11. When Patrick Dempsey first auditioned, he was terrified of Rhimes because of her stone-cold expression.

12. But Rhimes was actually trying to figure out what she could write for the, in her words, “dreamy” actor. ABC via no-one-tells-me-who-i-love.tumblr.com

13. James Pickens Jr. got the part of Dr. Richard Webber just minutes after he auditioned. After he read, they asked him to step into the hall, and when they brought him back in, he was offered the part.

14. Isaiah Washington originally auditioned for the role of Dr. Derek Shepherd.

15. Though Washington didn’t win that part, he got a call that the actor who had signed on to play Dr. Preston Burke had to drop out and the writers wanted him for the part.

16. The character Alex Karev (Justin Chambers) was added to the script after the pilot had already been shot, so all of his scenes were digitally implanted into the episode.

17. Rhimes started Meredith, Cristina, Alex, George, and Izzie as interns instead of established surgeons because she thought “there’s something really horrible about not knowing what you’re doing for a living.”

18. Pompeo didn’t know that Derek was married until the Season 1 finale was being filmed.

19. And Dempsey didn’t know his character was married until halfway through the first season.

​20. Kate Walsh was initially hired for only a few episodes, but she had such great chemistry with the cast that she was brought on full time and eventually given her own spin-off, Private Practice.